1. Technical Field
This invention relates to a pneumatically operated stepping valve for an automatic control of fluid inlets and fluid outlets in response to feedback signals indicating that an operation controlled by the valve has been completed. An inlet through passage and an associated outlet through passage formed in a valve disc are used to select a fluid inlet and a fluid outlet. Manual control elements are provided in the form of switches and pushbuttons acting on control levers, pawls, valves and pistons so that various modes of operation can be performed by the stepping valve. Indicating means are provided for a digital indication of the position of the valve and for an indication of pressure applied to the inlet line and outlet line.
Stepping selector valves of this kind are used, e.g., for an automatic control of pneumatically controlled operations which are to be performed in a predetermined sequence. In that case the next program step or operation must not be initiated until the preceding operation has been completed and a corresponding feedback signal has been received.
Manual operations are also required for setting up such automatic control systems. Such manual operations may be used to initiate only individual steps or to cause a repetition of certain sequences of steps called for by the program. It is also known to indicate the position of the valve in order to facilitate the setting up of equipment for a programmed sequence of operations.
2. Description of the Prior Art
Laid-open German Application 19 06 944 discloses methods and equipment for an automatic sequential control of consecutive operations to be performed by pneumatically controlled systems. Such control systems are composed of a large number of pneumatically controlled switching and logic elements. Said systems can be designed exactly for each application but are highly expensive. Besides, such stepping control systems are bulky and can be designed only by experts who are familiar with and have experience in the design of such control systems and in the selection of the dimensions of their components.
Laid-open German Application 19 37 697 discloses selecting values for an automatic control of consecutive operations. Said known valves constitute compact units and are highly expensive. They are made of metal elements and their application is restricted by their high costs. Said known valves comprise a valve body and a rotatable valve disc, and the sealing surfaces of said valve body and rotatable valve disc are urged against each other by springs. As a result, large forces are required to shift the rotatable valve disc, and the drive means required for that purpose involve a correspondingly high structural expenditure. Said known valves are also bulky and involve a relatively high expenditure for the functional control of the valve itself.